Synthetic or Conventional Oil?

Traditional wisdom tells us that a synthetic creation is usually not quite as good as the original it strives to emulate. (The difference between clothing made of polyester versus silk comes to mind.) Does that same truism apply to synthetic oil, when compared to automotive oil derived from crude?

Fundamentals
To grasp this slippery subject, we first need to cover some fundamentals. Synthetic oils are a result of scientific manipulation of non-conventional fluids, but here the silk-or-polyester analogy stops. Synthetic oils are definitely not the equivalent of polyester leisure suits; in fact, they are generally priced three to four times that of conventional oil. And, more to the point, synthetics are an improvement over their conventional kin.


Let's break down the details of synthetics, and what makes them better. One definition of "synthetic" is big molecules built up from small ones. Like genetic engineers, the oil companies figured they could improve the performance of engine oil and eliminate some of the shortcomings in the laboratory.


In the simplest terms, the base stock of synthetics, polyalphaolefin (PAO) starts as ethylene gas, a simple two-carbon molecule that is built up to a 10-carbon molecule. Three of these super molecules are combined to form PAO, a base stock that offers a number of advantages over Mother Nature's version. Synthetics are more stable, flow at lower temperatures, are more resistant to boiling off, and less susceptible to oxidation, which causes thickening with prolonged high temperatures.


The inherent element with crude stock for motor oil is the molecular construction. Conventional motor oil is a batch of short-chain and long-chair carbon and hydrogen atoms. In extreme heat, the short chains can evaporate and these unstable molecules oxidize and break down. In addition, contaminants and reactive and/or unstable hydrocarbons can sneak through the refining process.